I have a 75gal I believe it is an all glass aquarium, which i bought new about 10 years ago. It did make one local move about 3 years ago just within the same town. Anyways -- I have 2 cracks in the black plastic rim on the top one in the front and one in the back. I believe that they have been there for quite awhile (months or possibly years). How much structural support do those top plastic rims provide? I am wondering if i should -- watch it, be concerned, be VERY CONCERNED or get another tank ASAP. I am leaning towards the watch it but was wondering if cracking of this black plastic is common due to heat from lamps and the saltwater that it comes in contact with.